1. Field of the Invention
The present invention relates generally to folders for printing presses and more particularly to a folding cylinder for a cross-folder.
2. Background Information
Web printing presses print a continuous web of material, such as paper. In a folder of the printing press, the continuous web then is cut into signatures in a cutting unit and folded. One possible fold to the resulting signatures is a cross-fold perpendicular to the direction of movement of the signatures. A tucking cylinder generally will hold a lead edge of a signature with a pin or gripper, either before or after the signature has been cut from the web. A tucking mechanism in the tucking cylinder may then tuck the signature at a mid-point into a jaw of a jaw cylinder or into folding rolls so as to provide a cross-fold.
U.S. Pat. Nos. 5,102,111 and 5,484,270 for example disclose cross-folding folders having tucking cylinders. A web is received between a cutting cylinder and the tucking cylinder to form signatures, the lead edge of the signatures being held by pins. Tucking blades in the cylinders tuck the signatures into jaws of a jaw cylinder.
U.S. Pat. No. 6,038,974, which is not necessarily prior art to the present invention, discloses a cross folder for receiving signatures in grippers. The folder thus could be used with either a web or sheet-fed printing press. A jaw cylinder and tucking cylinder combination provide the cross-fold.
For cutting webs and tucking and transporting signatures, it is often desirable to vary the outer effective diameter of the tucking cylinder to permit proper processing of variable-thickness signatures. Signature width may vary significantly depending on the desired end product. It thus has been known to provide so-called expansion segments on a tucking cylinder, the expansion segments being adjustable by a cam/spring mechanism to vary the effective outer diameter of the tucking cylinder.
However, it has been found that these expansion segments or their supports can be damaged easily, especially during paper jams on one side of the pin cylinder, for example the work side or the gear side.